Combined compressing apparatus

ABSTRACT

In a scroll compressor, a fixed wrap of a fixed end plate engages with an orbiting wrap of an orbiting plate to form a compressing chamber. A gas is introduced into the compressing chamber from the outer circumference and compressed towards the center as the orbiting end plate revolves with a driving shaft with respect to the fixed end plate. The gas is sent to a reciprocating compressor in which a piston moves up and down in a cylinder and further compressed therein.

BACKGROUND OF THE INVENTION

The present invention relates to a combined compressing apparatuscompressing in a downstream compressor a compressed gas discharged froman upstream compressor.

JP2703319B2 discloses a combined compressing apparatus in which aturbo-type compressor is used as an upstream compressor and avolume-type compressor such as a reciprocating compressor or a scrollcompressor is used as a downstream compressor. A primary compressed gasin the turbo-type compressor is forwarded to the volume-type compressorin which a primary compressed gas is further compressed and dischargedas a secondary high-pressure compressed gas.

However, in a known combined compressing apparatus, a massivelow-pressure compressed gas is discharged from the turbo-type compressoras upstream compressor, so that a large volume-type compressor is usedto suck the primary massive compressed gas from the turbo-typecompressor to make its size larger and make power load increased.

SUMMARY OF THE INVENTION

In view of the disadvantages in the prior art, it is an object of theinvention to provide a combined compressing apparatus which makes itssize smaller and makes power load decreased thereby producing ahigh-pressure compressed gas effectively.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the invention will become more apparentfrom the following description with respect to embodiments as shown inaccompanying drawings wherein:

FIG. 1 is a schematic view of a combined compressing apparatus accordingto the present invention;

FIG. 2 is a vertical sectional view of the first embodiment of acombined compressing apparatus according to the present invention; and

FIG. 3 is a vertical sectional view of the second embodiment of acombined compressing apparatus according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As shown in FIG. 1, in a combined compressor according to the presentinvention, a scroll compressor 1 that is excellent in quietness andsaving energy is employed as upstream compressor and a reciprocatingcompressor 2 that is simple in structure and can supply high pressure isemployed as downstream compressor. A primary compressed gas A compressedby the scroll compressor 1 is sent to the reciprocating compressor 2, bywhich the primary compressed gas A is further compressed to a highpressure secondary compressed gas B which is sent to a tank 3.

In FIG. 2, the first embodiment of a combined compressing apparatus isshown in which the rear of a cylindrical housing 11 of the scrollcompressor 1 is fixed to the front of a crank case 22 of thereciprocating compressor 2. A single motor 4 is mounted to the rear ofthe crank case 22. The motor 4 acts as power source for driving thescroll compressor 1 and the reciprocating compressor 2.

The scroll compressor 1 comprises an involute fixed wrap 13 in thesealed housing 11 and an orbiting wrap 15 which engages with the fixedwrap 13 to form a compressing chamber 16.

The fixed wrap 13 is provided on the rear surface of a fixed end plate12, while the orbiting wrap 15 is provided on an orbiting plate 14rotatably mounted in the housing 11.

The orbiting plate 14 is rotatably mounted to an eccentric axial portion42 of a driving shaft 41 which passes through a center of a cover 24closing the rear surface of the housing 11 and is rotated by a motor 4.The cover 24 is also part of the crank case 22 of the reciprocatingcompressor 2. The orbiting plate 14 is eccentrically revolved withrotation of the driving shaft 41 and connected to the cover 24 withthree pin-crank-type self-rotation preventing devices 17 positioned on acircle.

In the outer circumference and center of the fixed end plate 12 of thehousing 11, there are a scroll inlet 111 for sucking an external gasinto the compressing chamber 16 and a scroll outlet 112 for discharginga primary compressed gas A compressed in the compressing chamber 16respectively.

When the orbiting end plate 14 is eccentrically revolved by the motor 4,the compressing chamber 16 defined by the fixed wrap 13 and the orbitingwrap 15 gradually reduces in volume from the outer circumference to thecenter. Thus, the external gas sucked from the scroll inlet 111 isgradually compressed towards the center and the primary compressed gas Ais discharged from the scroll outlet 112. The primary compressed gas Afrom the scroll outlet 112 is forwarded to the reciprocating compressor2 and partially introduced into the crank case 22 of the reciprocatingcompressor 2.

In the reciprocating compressor 2, a piston 23 reciprocates in acylinder 21 to suck and discharge a gas over and over. On the cylinder23, there are a cylinder inlet 25 for introducing the primary compressedgas A discharged from the scroll outlet 112 into the cylinder 21 and acylinder outlet 26 for discharging a secondary compressed gas Bcompressed in the cylinder 21.

The piston 23 is reciprocated in the cylinder 21 with a crank shaft 43of the driving shaft 41 driven by the motor 4 via a piston rod 27.

In the upper part of the crank case 22, there is a crank-case inlet 221for partially sucking the primary compressed gas A discharged from thescroll outlet 112 into the crank case 22.

The piston 23 reciprocates in the cylinder 21, so that the primarycompressed gas A is introduced from the cylinder inlet 25 via a suctionvalve 28 over the piston 23 in the cylinder 21 and further compressed.Then, high-pressure secondary compressed gas B is discharged from thecylinder outlet 26 via a discharge valve 26 and sent to the tank 3.

During reciprocating motion of the piston 23, the primary compressed gasA discharged from the scroll outlet 112 of the scroll compressor 1 ispartially introduced into the crank case 22 to allow the inside of thecrank case 22 to be pressured to more than atmospheric pressure. Thus,difference in pressure between the compressed gas in the compressingchamber on the piston 23 and that in the crank case 22 is smaller thanwhat has about atmospheric pressure in the crank case 22. Therefore, ifdifference in pressure between the upper surface and lower surfaces ofthe piston 23 is great, rapid and strong downward force acts onto thepiston 23, so that excessive and unequal force is applied to the outercircumferential surface of the piston 23, the piston ring, a bearing anda sealing portion thereby causing early malfunction. In the embodimentof the present invention, difference in pressure becomes smaller toavoid the cause of early malfunction thereby discharging smallerhigh-pressure compressed gas efficiently.

In the first embodiment, the primary compressed gas A compressed in thescroll compressor 1 excellent in quietness and energy saving is furthercompressed in the reciprocating compressor 2 which is simple instructure and possesses high-pressure availability to allow thesecondary high-pressure compressed gas B to be discharged. The scrollcompressor 1 is driven together with the reciprocating compressor 2 bythe single motor 4, thereby reducing size and saving cost. Furthermore,as mentioned above, the primary compressed gas A discharged from thescroll outlet 112 of the scroll compressor 1 is partially introducedinto the crank case 22 thereby reducing size of the reciprocatingcompressor 2 and improving quietness.

In the second embodiment of a combined compressing apparatus in FIG. 3,a scroll compressor 1 and a reciprocating compressor 3 comprise motors4,5 respectively as power source. On the way of a fluid path throughwhich a primary compressed gas A compressed in the scroll compressor 1is forwarded to a cylinder inlet 25 of the reciprocating compressor 2, aselector valve 6 is provided. Except them, it is similar to those in thefirst embodiment. The same numerals are allotted to the same members asthose in the first embodiment and its description is omitted.

A motor 5 for driving the scroll compressor 1 is mounted in front of asealed cylindrical housing 11. An orbiting plate 14 having an orbitingwrap 15 is rotatably mounted to an eccentric axial portion 52 of adriving shaft 51 driven by a motor 5 and going through the center of acover 18 of the housing 11, and connected to the cover 18 via apin-crank-type self-rotation preventing device 17 to eccentricallyrevolve with rotation of the driving shaft 51.

On the upper part of the housing 11 and through the center of the fixedend plate 12, there are a scroll inlet 111A for sucking an external gasinto the compressing chamber 16 and a scroll outlet 112A for discharginga primary compressed gas compressed by the compressing chamber 16 tointroduce it into a crank case 22 of the reciprocating compressor 2.

The primary compressed gas A discharged from the scroll outlet 112A isintroduced into the crank case 22 through a through hole 44 extendingaxially towards the end of the driving shaft 41 of the motor 4.

On the upper part of the crank case 22, there is formed a crank-caseoutlet 222 for discharging the primary compressed gas A introduced intothe crank case 22 and forwarding it into the cylinder inlet 25.

A selector valve 6 is provided on the way of the fluid path between thecrank-case outlet 222 and the cylinder inlet 25 to enable the selectorvalve 6 to be switched to a first fluid path 9 for forwarding theprimary compressed gas A discharged from the crank-case outlet 222 tothe cylinder inlet 25 or to a second fluid path 10 for forwarding it toa downstream side of the cylinder outlet 26, going around thereciprocating compressor 2.

The selector valve 6 is switched by a control device 7 having anelectric circuit, and the motors 4,5 are driven, stopped and controlledby the control device 7. A pressure sensor 8 for measuring pressure in atank 3 is provided at the downstream side of the cylinder outlet 26.Information such as measured value by the pressure sensor 8 istransmitted to the control device 7 which stops when compressed gas inthe tank 3 reduces in consumed amount to allow compressed gas forwardedto the tank 3 to increase.

To require a secondary high-pressure compressed gas B, a switch (notshown) for the control device 7 is switched to a high-pressure side.Thus, the first fluid path 9 of the selector valve 6 is opened, whilethe second fluid path 10 is closed thereby allowing the motors 4,5 to bedriven together.

As a result, the scroll compressor 1 and reciprocating compressor 2 areboth actuated, so that the primary compressed gas A compressed in thescroll compressor 1 is introduced into the crank case 22 through thescroll outlet 112A and the through hole 44 and discharged from thecrank-case outlet 222.

The primary compressed gas A from the crank-case outlet 222 is forwardedto the cylinder inlet 25 through the selector valve 6 and the firstfluid path 9 and introduced into the cylinder 21. Thus, the secondaryhigh-pressure compressed gas B is discharged from the cylinder outlet26.

To require a primary low-pressure compressed gas A, the switch of thecontrol device 7 is switched to a low-pressure side. Thus, a solenoid 61of the selector valve 6 is magnetized to close the first fluid path 9 ofthe selector valve 6 and to open the second fluid path 10 and drivesonly the motor 5. As a result, the scroll compressor 1 is only operated,so that a primary compressed gas A compressed in the scroll compressor 1is introduced into the crank case 22 through the scroll outlet 112A andthe through hole 44 and is discharged from the crank-case outlet 222.And the primary compressed gas A discharged from the crank-case outlet222 is not forwarded to the cylinder inlet 25, but is forwarded to thedownstream side of the cylinder outlet 26 through the selector valve 6and the second fluid path 10.

In the second embodiment, the secondary high-pressure compressed gas canbe effectively obtained similar to the first embodiment. The primarycompressed gas A compressed in the scroll compressor 1 is introducedinto the crank case 22 thereby allowing the reciprocating compressor 2to become smaller and improving quietness. Also, by switching theselector valve 6, the primary low-pressure compressed gas A and thesecondary compressed gas B can be selectively obtained if required.Especially, when the primary low-pressure compressed gas A is required,the reciprocating compressor 2 stops to let the scroll compressor 1driven only thereby improving quietness and energy saving.

The embodiments of the present invention are described and the followingchanges and modifications may be made without departing from the scopeof claims below.

-   -   (i) The primary compressed gas A compressed and discharged in        the scroll compressor 1 in the first embodiment is directly        introduced into the crank case 22 of the reciprocating        compressor 2 as described in the second embodiment. And the        primary compressed gas A introduced in the crank case 22 is        discharged from the crank case 22 and forwarded to the cylinder        inlet 25.    -   (ii) The primary compressed gas A compressed in and discharged        from the scroll compressor 1 in the second embodiment is        partially introduced into the crank case 22 of the reciprocating        compressor as described in the first embodiment.    -   (iii) In the second embodiment, the selector valve 6 allows the        first fluid path 9 to close and the second fluid path 10 to open        based on a measured value higher than a certain value by the        pressure sensor 8 measuring pressure in the tank 6 storing the        secondary compressed gas B discharged from the cylinder outlet        26 of the reciprocating compressor 2, while the selector valve 6        allows the first fluid path 9 to open and the second fluid path        10 to close based on a measured value lower than a certain value        by the pressure sensor 8.

1. A combined compressing apparatus comprising: a scroll compressorcomprising a driving shaft, a fixed end plate and an orbiting platerotatably mounted to the driving shaft, a fixed wrap of the fixed endplate engaging with an orbiting wrap of the orbiting end plate to form acompressing chamber, the orbiting plate that revolves with respect tothe fixed end plate with rotation of the driving shaft compressing a gasintroduced through a scroll inlet in the outer circumference of thefixed end plate towards a center to discharge a primary compressed gasthrough a scroll outlet at the center; and a reciprocating compressorcomprising a cylinder and a piston moving up and down in the cylinder,said cylinder having a cylinder inlet and a cylinder outlet, thecylinder inlet being connected to the scroll outlet to enable theprimary compressed gas to be introduced into the cylinder and to becompressed by reciprocating the piston in the cylinder.
 2. A combinedcompressing apparatus of claim 1 wherein the reciprocating compressorfurther comprises a crank case, a piston rod mounted to a lower surfaceof the piston in the crank case and a crank shaft connected to a lowerpart of the piston rod in the crank case.
 3. A combined compressingapparatus of claim 2 wherein the scroll compressor and the reciprocatingcompressor are driven by a single power source.
 4. A combinedcompressing apparatus of claim 3 wherein the power source comprises amotor.
 5. A combined compressing apparatus of claim 2 wherein the scrolloutlet is also connected to a crank-case inlet of the crank case toallow the primary compressed gas to be introduced into the crank case toincrease internal pressure in the crank case.
 6. A combined compressingapparatus of claim 3 wherein the driving shaft that drives the orbitingplate is connected to the crank shaft of the reciprocating compressor toallow the scroll and reciprocating compressors to be driven together. 7.A combined compressing apparatus of claim 1 wherein the scrollcompressor and the reciprocating compressor are driven by first andsecond power sources respectively.
 8. A combined compressing apparatusof claim 7 wherein the power source comprises a motor.
 9. A combinedcompressing apparatus of claim 7, further comprising a selector valve ona flow path of the primary compressed gas from the scroll compressor tothe reciprocating compressor to switch whether the primary compressedgas goes to the reciprocating compressor or is directly dischargedwithout going to the reciprocating compressor.
 10. A combinedcompressing apparatus of claim 9, further comprising a control deviceconnected to the selector valve to switch whether or not the primarycompressed gas should be sent to the reciprocating compressor.
 11. Acombined compressing apparatus of claim 10, further comprising a tankthat receives finally compressed gas and a pressure sensor that measurespressure in the tank, said pressure sensor being connected to thecontrol device to send the control device information of the pressure inthe tank to decide whether or not the primary compressed gas should befurther compressed in the reciprocating compressor.
 12. A combinedcompressing apparatus of claim 8 wherein the scroll compressorcommunicates with the crank case through a though hole along a centralaxis of the scroll compressor.
 13. A combined compressing apparatus ofclaim 10 wherein the control device is connected to the first powersource and the second power source when one of the scroll anreciprocating compressors is required to stop by stopping one of thefirst and second power sources connected to the scroll and reciprocatingcompressors.